Feraz N. Rahman MS, Presenter: Nothing to Disclose

Jeffrey Keith Smith MD, PhD, Abstract Co-Author: Nothing to Disclose

Elizabeth Bullitt MD, Abstract Co-Author: Potential license agreement, W. L. Gore & Associates, Inc Potential license agreement, Kitware Inc

Laurence Katz MD, Abstract Co-Author: Nothing to Disclose

Bonita L. Marks PhD, Abstract Co-Author: Nothing to Disclose

Our brains undergo cognitive decline and physical changes with aging. Altered cerebral vasculature such as the narrowing and loss of small vessels may contribute. Exercise reverses small vessel disease elsewhere in the body and increases brain volume and cognitive function in the elderly. Previously, we reported that cerebral blood flow(CBF) in older adults is more variable in those who exercise less. This study aimed to test the hypothesis that there are less small cerebral arteries in that group. A secondary aim was to examine relationships between CBF and vasculature and how they are affected by exercise.

Subjects: 12 healthy adults 60-76 years old underwent CBF and MR angiogram(MRA) scans. Over the last 10 years, 6 exercised over 3 hours/week(Active Group) and 6 less than 1 hr/wk(Inactive Group) in aerobic sports. MR Imaging: 3.0T MRI was used to acquire CBF scans(continuous arterial spin labeling, TR=4000,TE=16ms) and time of flight MR angiograms(TR=35,TE=3ms,voxels=0.5x0.5x0.8mm). Data Analysis: Vessels were segmented from MRA by software that extracts intensity ridges from user-defined seed points. Mean CBF for each major vascular distribution was calculated by Matlab software and correlated in the same region with average vessel radius(AVR), number, and tortuosity. Vessel radii were plotted as histograms and the 2 groups compared based on subsets of vessel size by 2-sample t-test and Wilcoxon rank sum.

A positive correlation existed between CBF and AVR in the Active Group(0.55,p<0.01). A negative correlation existed, however, in the Inactive Group(-0.62,p<0.01). The number of small vessels(AVR<0.35mm) was higher in the Active Group compared to the Inactive Group(mean ±standard deviation=211±45 vs. 161±29,p<0.05).

Inactive subjects had fewer cerebral small vessels than the active group. In active subjects, CBF positively correlates with AVR. In inactive subjects, however, the correlation is negative. These findings could be explained by greater small vessel loss in the Inactive Group. With fewer small vessels, the AVR in a given vascular tree increases along with vascular resistance leading to decreased CBF.   supp. by R01EB000219NIH-NIBIB  

An aerobic exercise program may be a vital part of healthy aging by preventing the narrowing and loss of small cerebral blood vessels and consequent decrease in cerebral blood flow.

Rahman, F, Smith, J, Bullitt, E, Katz, L, Marks, B, Relationship of Exercise to Cerebral Vasculature and Blood Flow in Older Adults.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6009535.html